The spatial and seasonal patterns and stability of the Lake Whitefish fishery in Michigan waters of southern Lake Huron

Abstract Objective Given that the harvested fish from five separate fishing grounds belong to one large mixed population, our objective is to develop an overall abundance index for Lake Whitefish Coregonus clupeaformis in Michigan waters of southern Lake Huron. Methods We analyzed catch-and-effort data for individual fishing trips to five separate fishing grounds and used Bayesian information criterion to select the best model struture. Result The best model included the year × area × month interaction as a random effect, representing the random component in fishery dynamics that were influenced by both fishing practices and fish abundance. The best model also included the fixed effects of area × month interaction, a result consistent with our hypothesis that the seasonal spatial migrations of Lake Whitefish provide the links among the fisheries in separate fishing grounds, and the fishery yields from these separate areas were all dependent on the production in southern Lake Huron as a whole. After adjusting for the random effect of year × area × month interaction and the fixed effects of area × month interaction, the estimated patterns for the fixed year effect indicated that the Lake Whitefish abundance in Michigan waters of southern Lake Huron declined during the late 2000s but has been relatively constant after 2012. Conclusion The declines in annual fishery yield were due to and could be explained more by the decreases in fish abundance through 2012 but thereafter primarily reflected the declines in annual fishing effort as the fisheries continued to adjust to the changed fishing conditions. We also provided general lessons for studying fisheries without fishery independent surveys but with detailed seasonal and spatial catch-and-effort data.